The subject matter of the present disclosure relates generally to systems and methods for proximity sensors. In particular, the subject matter relates to inductive proximity sensor configurations for minimizing false readings and improving performance.
Conventional inductive proximity sensors are generally known for sensing the presence of targets of interest in a sensing region. Such devices typically include an LC tuned oscillator for producing an oscillating electromagnetic field around a sensing coil. The sensing coil may typically have a ferrite core, which may have a T-shaped or E-shaped cross section. The ferrite core may shape and extend the electromagnetic field surrounding the ferrite core in a sensing direction and/or concentrate or channel the electromagnetic field in other directions, such as behind and to the sides of the coil. A target which enters the sensing region of the proximity sensor may disrupt the electromagnetic field around the sensing coil with an eddy current and change the impedance of the coil sufficiently to alter the oscillating state of the LC oscillator. A proximity sensor may include an evaluator circuit having control circuitry for providing feedback indicative of the presence of a target of interest.
While advances have been made in the design of proximity sensors, such as to improve their sensing range and sensitivity, conventional proximity sensors may not perform consistently in certain applications. For example, inductive proximity sensors may often be used to detect the presence of different targets composed of various materials. However, different targets (e.g., ferrous targets and non-ferrous targets) typically have different effects on the impedance of the sensing coil, resulting in different sensing distance ratios for different materials (e.g., metals). Furthermore, inductive proximity sensors are often influenced by rapid changes in an environment surrounding the sensor (e.g., rapid temperature changes). Changes in the surrounding environment may influence the performance of the sensors, such as by changing a temperature of a single element of the sensor. For example, a face of the sensor may change temperatures before other elements of the sensor change. The resulting temperature difference may induce variations in the eddy currents that interact with the magnetic field of the sensing coil. As the face of the sensor is closer than a target of interest, the proximity sensor may sometimes return a fault trigger, where the face is sensed, rather than the target of interest. Thus, changes in the surrounding environment may induce false readings or false detections of targets. The subject matter of the present disclosure may limit effects of the environment on the sensor while detecting the target and improve sensing performance (e.g., provide an increased sensing range).